1. Field of the Invention
This invention relates to a gas compressor which receives compressive power from outside through an electro-magnetic clutch and to an air conditioning system having this gas compressor.
2. Description of the Related Art
Many of the vane-rotary-type gas compressors, scroll-type gas compressors, swash-plate-type gas compressors, etc. used in automotive air conditioners, GHP or the like, receive drive power from outside through an electro-magnetic clutch. An example in which an electro-magnetic clutch is used in a vane-rotary-type gas compressor will be described with reference to FIGS. 1 and 2. An electro-magnetic clutch 10 is mounted to a case cover 23 provided in the outer periphery of one end portion of a rotor shaft 22 retaining a rotor 21 equipped with vanes 20. More specifically, stationary portions of the electro-magnetic clutch 10 which do not rotate, that is, an annular core 11 and a coil 12 provided inside the core 11, are mounted to an intermediate shoulder end surface 23a of the case cover 23 by means of a retaining ring 13a through the intermediation of a core flange portion 13 of the core 11. The core flange portion 13 has a protrusion 13b, which is fitted into a recess 23b of the intermediate shoulder end surface 23a of the above-mentioned case cover to thereby prevent rotation of the core 11.
Further, in the rotatable driven portion of the electro-magnetic clutch, an armature friction plate 14, a buckling 15, an elastic coupling body 16, a base plate 17, and a hub 18 are connected together. The hub 18 is further connected to the rotor shaft 22.
The manner in which the above-mentioned components are connected will be described more specifically. The armature friction plate 14 and the buckling 15 are connected to each other by means of a plurality of joint pins 15a. The buckling 15 and the base plate 17 are integrally connected to each other by the elastic coupling body 16, which is formed of torsional rubber. When the armature friction plate 14 is attracted by the magnetic force of the clutch, the elastic coupling body 16 undergoes elastic deformation. The base plate 17 and the hub 18 are connected to each other by means of a plurality of joint pins 17a. The hub 18 is fastened to one end of the rotor shaft 22 by means of a spline 24 so as to be connected to a compressor main body 25 side.
The rotatable driving portion of the electro-magnetic clutch comprises a pulley 26 formed of a magnetic material, and this pulley 26 is mounted to the case cover 23 through the intermediation of a ball bearing 27.
In the pulley 26, an inner peripheral portion 26a forming a bearing housing and an outer peripheral portion 26c having pulley grooves 26b in the outer periphery thereof are connected to each other on a pulley end surface 26d side so as to define a U-shaped sectional configuration, and the core 11 is accommodated in the recess thus defined. Numeral 19 indicates holes for forming a magnetic circuit between the armature friction plate 14 and the pulley 26.
When the above-described gas compressor is used in an automotive air conditioner, the pulley 26 on the driving side is rotated by a belt (not shown) entrained about it and about the output shaft of the engine. When the electro-magnetic clutch 10 is not energized, the armature friction plate 14 on the driven side is spaced apart from the pulley 26, and does not rotate. In this state, the gas compressor is at rest.
When electric current is supplied to the coil 12 of the electro-magnetic clutch 10 to energize the same, the armature friction plate 14 is attracted by the end surface 26d of the pulley 26 due to the magnetic flux of the coil, whereby the driving side and the driven side of the electro-magnetic clutch 10 are integrated with each other, causing the rotor shaft 22 to rotate. In this state, the gas compressor is operating, with the elastic coupling body 16 undergoing elastic deformation.
In the conventional gas compressor, burning of the electro-magnetic clutch or rupture of the belt can happen during operation, though on rare occasions. On examination, it has been found that such trouble is attributable to the following phenomena.
(1) Anomalous Heat Generation of the Ball Bearing 27
When the ball bearing 27 generates more heat than usual due to poor lubrication, wear, etc. and attains a high temperature as shown in FIG. 7, the heat is transmitted to the core 11 of the electro-magnetic clutch 10, which is beside the ball bearing surface and which surrounds the outer periphery of the bearing, and the core 11 also attains a high temperature, with the result that the mold thereof is melted, which may cause short-circuiting of the wiring. Further, the coil 12 and the portion of the pulley 26 near the end friction surface 26d also attain a high temperature, resulting in a reduction in the magnetomotive force of the electro-magnetic clutch 10, as shown in FIG. 8.
The reduction in the magnetomotive force weakens the attracting force acting between the pulley 26 and the armature friction plate 14, and slippage occurs therebetween, thereby generating sparks. Further, the frictional heat generated causes an increase in the ambient temperature, thereby destroying the elastic coupling body 16made of rubber. In this state, the armature friction plate 14 comes into contact with the hub 18, and frictional heat is generated to thereby generate sparks, with the result that the core 11 undergoes further temperature rise. Further, the rotor shaft 22 ceases to rotate in the normal manner.
When the temperature of the core 11 exceeds 200xc2x0 C., the mold is softened and melted. If such an acute temperature rise can be detected before this temperature level is reached, this trouble could be prevented.
(2) Anomalous Heat Generation of the Electro-magnetic Clutch
When rotation is continued after the breakage of the ball bearing 27, the core 11 and the pulley 26, which are spaced apart from each other by a small gap, come into contact with each other, and the resultant frictional heat causes a rapid temperature rise in the core 11. In this case also, the mold is melted, the wiring is short-circuited, or the magnetomotive force is reduced. The trouble caused in this case is the same as that in the above-described phenomenon (1).
When the ball bearing 27 is eventually locked as a result of breakage, slippage occurs between the pulley 26 and the belt, and the resultant frictional heat will damage and rupture the belt.
Even when the ball bearing 27 is in the normal condition, heat generation in the core 11 can happen as a result of short-circuiting of the wiring.
(3) Clutch Slippage
Further, during the operation of the electro--magnetic clutch, clutch slippage, i.e., slippage between the pulley end surface 26d and the armature friction plate 14, occurs. As is well known, this slippage mitigates the shock at the time of start-up, allowing the system to start smoothly. Repetition of start-up operation leads to gradual wear of the contact surface of the armature friction plate 14. Further, even when the gas compressor is performing normal operation, minute slippage occurs as a result of fluctuations in load in rotor rotation, momentary overload, etc.
Clutch slippage naturally involves heat generation. An abnormal increase in the slippage between the pulley end surface 26d and the armature friction plate 14 as a result of wear of the armature friction plate 14, etc. causes an increase in slippage and heat generation, which can damage the contact surfaces and fuse them together. Damage to the contact surfaces will cause a further increase in clutch slippage or make them incapable of coming into contact with each other, which means the engagement of the clutch cannot be effected. Fusion of the contact surfaces makes it impossible to effect disengagement of the clutch.
It is to be noted, however, that anomalous clutch slippage is accompanied by radiation of heat and generation of sparks due to anomalous heat generation, which means the above trouble could be prevented if these phenomena can be detected.
This invention has been made in order to solve the above problem in the prior art. It is accordingly an object of this invention to provide a gas compressor and an air conditioning system in which it is possible to detect an abnormal temperature rise in the electro-magnetic clutch at an early stage to stop the energization thereof or stop the operation of the air conditioning system as a whole.
To achieve the above object, there is provided, in accordance with this invention, a gas compressor of the type in which external power is transmitted to the compressor main body through an electro-magnetic clutch, wherein a temperature sensor is mounted to the outer surface of the electro-magnetic clutch or to a portion near the outer surface thereof.
Since it is most desirable to detect the temperature of the armature friction plate, which generates heat as a result of slippage, and the temperature of the core or the ball bearing, which generates heat due to the load at the time of power transmission, the temperature sensor is preferably arranged in the vicinity of the armature friction plate or mounted to the core flange portion for mounting the electro-magnetic clutch or to a portion in the vicinity of the core or the ball bearing of the electro-magnetic clutch so as to be externally detachable.
In accordance with the present invention, there is further provided an air conditioning system of the type which includes a gas compressor in which external drive power is transmitted to the compressor main body through an electro-magnetic clutch, the air conditioning system comprising a temperature sensor mounted to the electro-magnetic clutch or to a portion in the vicinity thereof, an outlying temperature decision means for making a judgment as to whether the detection output of the temperature sensor is an anomalous value, and an emergency stop means which interrupts a driving circuit of the electro-magnetic clutch or stops the air conditioning system upon receiving an anomaly decision output from the outlying temperature decision means.